Concentric line oscillator



thefe is a oonductfve connection to the cathode can led...fn 2, and a copacitive coupling to the heater lead-ins 28 and 39, aS iS indicated by oon denSers and f.

The cathode iS pfeferably held af gfoond po tentfaL thfS being done InoSt oonveniently by n1eanS of a gfound oonnection o, 1ocated at a potential noda1 point on the auxiafy pipe 36. In this Way the gfound conneotion is nlade one of fnofe half fvave lengths electficaHy distant froln the cathode.

In order to perfnit the application of a desired gnd biaS to the gfid, the audHafy pipe 36 is prefefably bfoken at f, the bfeak being bfidged With feSpeot to radio frequency by a suitable capaoftonce indicafed at f8. Grid biaS n1ay be applied at Iead 1ooated betWeen the fadio fre quenoy conenSef and the grid. In the pfesent caSe, the gfid bias is developed aofosS a gfid bias fesiStof 52, Shunted by distributed of lumped capacitanoe 53.

The anode iS extended by n1eans of an anode pipe This iS preferably Inade of teleSoopicaHy related Seotfons 56 and thuS affording adjuSfnlent of the overan length of the anode and anode pipe to be an equivalent half Wave of the oscillation ffequency. ThiS iS fnost cleafly ShOWn in Figure 3, in Which it Wi11 be Seen that theTe is o standin Wave on the anode and anode pipe, in

dicated at The gfid and gfid pipe are also excited wfth a standing wave, but this iS oppo Site in p11aSe to the Standing Wave on the 9-flode plpe.

1)ifect anode potentia1 Inay be supplied in any deSifed fashion, bnt pfeferably by nleanS of a direct curfent Supply lead 2 (Fig. 1), connected at the ootential nodal point of anode pipe 5 f. Powel' nay be taken frofn the oscfllatol by nleanS of leadS Spaced Syfn!Tletfically about 9d nodal point in one of the ciTouits. In Figure 1 the tfansTniS Sion line leaoS are tapped onto the anode pipe on oppoSite Sides of the D. C. supply lead ef. In Pigufe 3, the power takeoff leadS 66 are diSposed on opposite Sides of the gfound The stfucfure of the vacuufn tube is shoWn in gfeafef detai1 in igufe 2, and feferfing to that ffguTe it wi11 be seen that both endS of the anode lB afe Stepped outWardly at f, and tapered to a feathered edge. T'hiS is sealed at 72 to glaSS ends and 2o. The end 2 is Sealed of to a sooket T6 foflning a part of a disk T8 on Which the gfid !4 is built. 1ofe Specincally, the grid consiStS of av Cage of axfa1ly-difected vVires vvhich are vvelded at one end to disk 78, and of the othef end to a fing an. Socket 76 iS internony threadeCf to receive the threaded end of gfid pipe 32.

The opposite glaSS end 8 has a reentrant stefn 82 Sealed to oenter lead-in 22 hich Suppofts the cothode oan f2. There afe alSo reentfanf stemS and 86 sealed to heatef 1eadinS 88 and 99, reSpectively. Lead-in 88 is connected to the end of a heater filafnent 92, o hile lead-in 90 iS connecfed to the end of a heater lafnent 94. The endS of the heatef maments 92 and 94 fnay be oonneoted directly to the closed end 9E of the cathode caf1. Iovvever, it iS desirable to prevent sogging of the fflaJIT1eflts caused by expanSion vvhen heated, for otherWiSe the fflan1ents fx1ay touch the cathode can, and vvhen, oS later descfibed, a conSidefable nuInbef of heat er 1an1entS avre eTnp1oyed, they Inay touch one anothef- To overcone this difcu1ty I connect the inner ends of the 1aInentS 92 and 94 to the anged end 98 of a Seeve lnu, Slidably caffied on center lead-if1 22. .A felatively 1ight oon1preSsion spfing 2 iS diSposed between the oppoSite end of Sleeve fa nd a conaf ln4, fixed on lead-iI1 22. Spfing m2 is So designed as to take up any sack oat1sed by expansion of the 1aInents when heated, and sucient cleaTance is provided between ange 98 and the closed end 96 of the cathode can to accon1Inodate the neceSSafy Inove ment.

In the particulaf stfucture hefe inuStfated thefe are Six heatef fllaInents, thfee of Wf1ich afe connected to eaoh of the lead-ins 88 and sn. The n1efhod of aocomphshing this may be deScfibed With fefefence to FigureS 6, 7, and 8. 'igufes 6 and 7 Show how lead-in 88 is provided vvith an eocentIfo coHar lna, vvhich in turn caffies tvvo addiona1 Supports lu8 and n. TheSe are ap pfopriately bent to provide three Suppoft points Sp3ced apaft.

It W be undefStood that the othe1 1ead-1 9 iS Sifflilarly provided vvith af1 eccentric coHof and tWo additional supports. The parts then of together in the manner shown in 'igue 8, in Whioh 1eadin 88, Wfth added SuppoftS lu8 and f o, is shown nested With lead-in 9 and its added SfppofS fl2 and In a11 thefe afe six supportS, dSpoSed 60 apaft, on an iInaginary circle 5, Said. cirole being concentfic with the oentef feadin 2, aund therefofe with the cathode can. All of the fJavfnentS afe connected at their outef endS to the 1aoent Supports, and are connected at fheinner ends to the ffange 98 (Figure 2) of the Spring pfeSSed sleeve leu,

he oo11p11g of the oathode to the shofting bar 38 hS been Sohen1atioaHy indicated in ,ig Llfe 1, and is shovvn in Structura1 forn1 i11 gufes and 5. The center lead-in 22 is feceived in a 1Tlef9u1lc buShing vvith a nletal-to-nletal con tact. The heater 1eadinS 88 and 9 are either nade 1ong enongh, of, as iS here inustrated, are fvelded to extensions l l8 and 2n, V f1ich alSo pasS through the bushing E. Howevef, theSe ead inS afe Sufrounded by inSulation tubes l22. efer1'ing to Pfgnre 3, the shorting bar 38 is a split bar, Whioh iS olaInped about the buShing s by 1eanS of a sofeW 2, vvhile itS oppoSite end is olan1ped about the auxiliafy pipe 36 by IneanS of a Sorev l2E. t vvi11 be evident that thefe is o r dfo ffequency coupling betvveen the cathode and the Shorting bar 38, thiS being provided by the oonduotive oonneotion to centef lead-in 22, nd by the capacitive ooupHng to the heater leadins. t i11 also be undefStood that shorting bar 38 is djustb1e a1ong bushing s and auxiHary pipe 3 for approprite tu1ing of the cathode to groond oonnection 44.

'The Elethod of enefgizing the fllanlents is illtfSffated in 'igI1re 1, in vvhich it vffi11 be Seen fht a 1ov freqoency alternating cuffent poWer Soo iS fecf through a transfornler !30 to the filafnef1t 1eadinS 28 and 39. ad1o ffequenoy choke f3f! fnoy be inSerfed. It WiH be evident that afnent 2 fs heated in SefieS fth fflafnent 2e, and that With six nlaInents afranged as prevfonSfy deSoribed, three of them are heated in pfneL and the tWo parane1 groups are oon necteo in Series.

Referring to Pigure 3, the anode pipe 56 is connected to the anode ls by nleans of a conar !3 ThiS iS preferably a Split collar, the halveS of WhiCh 1nay be placed about the anode and c1Tnped in poSition, as by n1eanS of eaTS '3G feceiving appropTiate Screvvs. Thepipe 5E is neoeSsarily S1ightly largef in dian1eter than the vaooom. fube vvith vvhfch it is 11Sed, but the in- 

